1. Field of the Invention
The invention generally relates to a driving circuit of a light emitting diode (LED), and more specifically, to a driving circuit for maintaining a current driving ability.
2. Description of Related Art
As concerns for environmental and energy preservation have drastically increased, the light emitting diode (LED) has gradually overtaken traditional incandescent light sources as the light source of the new millennium, owing to its small size, energy efficiency and durability. The LED emits light by converting electrical energy into light energy. Since an LED chip is made of semiconductor materials, the emitted wavelength is determined by the energy gap levels of the materials used, thereby allowing the LED to emit different colors of light. Therefore, not only can the LED be used as a white light source, but it may also be adopted as automobile headlights, traffic signals, text displays, billboards and other large displays, as well as regular and architectural lighting and backlights for a liquid crystal display (LCD), etc.
Since the emitted brightness of the LED is related with the size of the current conducted, the driving capability of the current is emphasized while driving the LED. Especially for large LED billboards, since the purpose is to display images or texts, the response time of the LED is of great importance. In large LED billboards, due to the large number of LEDs, a significant magnitude of current is needed for driving the billboards. If a driving circuit cannot provide enough current in time, then the LED might not be able to display accurate brightness and image quality. Therefore, for an LED display or billboard, a current driving ability of an LED driving circuit becomes a matter of great importance. However, conventional LED driving circuits mainly focus on current stability or driving voltage control, but few have placed emphasis on improving the driving ability of the driving current.